1. Field of the Invention
The present invention relates generally to an internal combustion engine of the type wherein coolant is boiled, so as to make use of the latent heat of vaporization of the coolant, and the coolant vapor is used as vehicle for removing heat from the engine, and more specifically to an improved coolant jacket arrangement therefor.
2. Description of the Prior Art
In currently used "water cooled" internal combustion engines, the engine coolant (liquid) is forcefully circulated by a water pump through a circuit including the engine coolant jacket and a radiator (usually fan cooled). However, in this type of system a drawback is encountered in that a large volume of water is required to be circulated between the radiator and the coolant jacket in order to remove the required amount of heat. Further, due to the large mass of water inherently required, the warm-up characteristics of the engine are undesirably sluggish. For example, if the temperature difference between the inlet and discharge ports of the coolant jacket is 4 degrees, the amount of heat which 1 Kg of water may effectively remove from the engine under such conditions is 4 Kcal. Accordingly, in the case of an engine having 1800 cc displacement (by way of example) is operated at full throttle, the cooling system is required to remove approximately 4000 Kcal/h. In order to acheive this a flow rate of 167 1/min (viz., 4000 -60.times.1/4) must be produced by the water pump. This of course undesirably consumes a number of horsepower.
In order to overcome this problem it has been proposed to boil the coolant and use the vapor as a heat transfer medium (thus taking advantage of the latent heat of evaporation of the coolant). Examples of such arrangements are found in U.S. Pat. No. 1,376,086 issued on Apr. 25, 1921 in the name of Fairman and in European Patent Application Publication No. 0059423 published on Sept. 8, 1982.
However, with such arrangements a problem has been encountered in that in zones of high heat flux such as in the immediate vicinity of the combustion chamber, exhaust port and valve, the vigorous boiling of the coolant in such zones tends to "bump" and produce a boiling froth or foam which gushes up out of the coolant jacket and spills or boils over into the condenser or radiator. As the foam contains quite a lot of liquid coolant the radiator tends to become wet and the heat exchange efficiency thereof markedly reduced. Viz., a film of liquid coolant tends to form on the inner walls of the radiator conduiting reducing the surface area via which the vapor may release its latent heat to the atmosphere. A further drawback encountered with this phenonomenon, is that the level of the coolant above the combustion chambers, exhaust ports and valves cannot be accurately detected due to the presence of the forth or foam and deluge of coolant.